The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Both the cost of delivering geometry data to a client device and the cost of rendering the geometry data into images affects the performance of vector image-driven applications, such as digital mapping applications. Efforts to minimize these two costs often result in pursuing conflicting objectives. For example, a more compact “encoding,” or representation, of polygon data may generate data that requires less network bandwidth for delivery (and less local storage), but the compact representation likely will be more computationally intensive to render. Conversely, polygon data sent to client devices as partially pre-rendered may ease the computational cost of rendering, while, at the same time, increasing the cost of data delivery.
The cost of delivering polygonal map features, such as parks, lakes and buildings, is frequently dominated by the delivery of coordinates which define the outline, or boundary, of these polygons. On a client device, polygons are often rendered in two steps: (i) the outline is stroked, and (ii) the interior of the polygon is filled. As such, it is sufficient, in some cases, to deliver just the outline of the polygon to the client. With this information, the client device may both stroke the outline and fill the interior. However, the latter step is typically accomplished via scanline rendering or triangle tessellation. Both of these approaches are computationally intensive and may seriously affect performance, particularly on low-powered client devices.